1. Field of the Invention
This invention relates to a document reproduction apparatus and in particular to a simple and inexpensive high-capacity output catch tray for document production devices such as copiers, printers and fax machines.
2. Description of Related Art
A. High Capacity Output Stacking Trays
In the prior art of output trays there has generally been an association of large, complex and expensive high volume copiers with similarly large, complex and expensive high capacity output collecting devices such as elevator trays, collators, sorters, vertically repositionable sheet output ports, and xe2x80x9cmailboxxe2x80x9d systems. In part this is because high volume copiers often must be capable of being coupled to subsequent machines in a production line, requiring that the top of the output stack be maintained at a relatively precise elevation for pickup by the next machine in the production line. However, where subsequent processing is not necessary there has previously been no simple, inexpensive, high capacity output stacking tray system available as a final station for such high volume copiers which did not suffer from various drawbacks addressed by the present invention.
Similarly, there has been an association of smaller, slower, and less expensive copiers with small, fixed, limited capacity output trays. High capacity output trays or systems with elevators or multiple trays generally either been unavailable for such smaller machines, or are too expensive to be suitable for the typical uses of such machines.
In all types of document production machines such as copiers, printers and fax machines, but particularly copiers for high speed, high volume production runs, the production of sheets by the copier can often exceed the capacity of presently available output catch tray systems. High capacity output trays, often referred to in the art as xe2x80x9cstackers,xe2x80x9d are particularly desirable for the collected output of high speed or plural job batching copiers or printers. High capacity stackers are also desirable for the accumulated output of unattended plural user (networked) copiers and printers, of any speed.
Further by way of background on sheet stacking difficulties in general, outputted sheets are usually ejected into an output tray from above one side thereof. Normal output stacking is by ejecting sheets or sets of sheets from above one side of the top sheet of the stack of sheets onto which that additional ejected sheet or set of sheets must also stack. Typically, sheets or sets are ejected generally horizontally (or slightly uphill initially) and continue to move horizontally primarily by inertia. That is, sheets or sets in the process of being stacked are not typically effectively controlled or guided once they are released into the output tray. The sheets or sets fall by gravity into the tray to settle onto the top of the stack. However, such settling is resisted by the relatively high air resistance of the sheet or set to movement in that direction. Yet, for high volume copiers stacking must be done at high speed, so a long settling time is undesirable. Thus, a long drop onto the stack is undesirable.
Stacking is made even more difficult where there are variations in thickness, material, weight and condition (such as curls) of the sheets. Different sizes or types of sheets, such as tabbed or cover sheets or Z-folded or other inserts, may even be intermixed in the stack. The ejection trajectory and stacking should thus accommodate the varying aerodynamic characteristics of such various rapidly moving sheets or sets. A fast moving sheet or set can act as a variable airfoil to aerodynamically affect the rise or fall of the lead edge of the sheet as it is ejected. This airfoil effect can be strongly affected by curls induced in the sheet, by fusing, color printing, etc. Therefore, an upward trajectory output angle and substantial release height is often provided, well above the top of the stack. Otherwise, the lead edge of the entering document can catch or snub on the top of the stack already in the output tray, and curl over, causing a serious jam condition. However, setting too high a document ejection level to accommodate all these possible stacking problems greatly increases the settling time for all sheets or sets and creates other potential problems, such as scattering.
Scatter within a stack causes at least four problems. First, if copier has a sets offsetting feature, intended to provide job set separations or distinctions, scatter within a stack makes such set distinction more difficult. Second, misaligned sheets or sets tend to incur damage such as bending, folding, abrasion or tearing of sheet edges out of alignment with the overall stack edge. Third, a substantial stack within which individual sheets are not well aligned to each other is more difficult for an operator to grasp and remove from the stacker. Fourth, a misaligned stack is not easily loaded into a box or other transporting container of corresponding dimensions.
For the above listed reasons, it may be seen that the top of stack elevation should be maintained within a desired range. A tray elevator or vertically repositionable sheet output port is therefore normally provided to maintain a relatively constant relationship of sheet output elevation to top of stack elevation for high capacity output trays.
Numerous means for dealing with various such general problems of sheet stacking are taught in U.S. Pat. Nos. 4,385,758, 4,469,319, 5,005,821, 5,014976, 5,014,977, 5,033,731, and art therein. Sheet xe2x80x9cknock downxe2x80x9d or settling assistance systems are known, but add cost and complexity and can undesirably prematurely deflect down the lead edge of the ejected sheet. Also, such xe2x80x9cknock downxe2x80x9d systems can interfere with sheet stack removal or loading and can be damaged thereby. Also, stacking systems should desirably provide relatively xe2x80x9copenxe2x80x9d trays, which will not interfere with open operator access to the output stacking tray or bin, for ease of removal of the sheet stack therein.
Many attempts have been made in the prior. art to provide high capacity sheet stacking output trays. Among these are: U.S. Pat. No. 5,609,333 (describing a sheet stack height control system); U.S. Pat. No. 5,318,401 (describing a stacking tray system with nonvertically receding elevator yielding square stacks); U.S. Pat. No. 5,346,203 (describing a high capacity sheet stacking system with variable height input and stacking registration); U.S. Pat. No. 4,329,046 (describing a method for operating a reproduction machine with unlimited catch tray for multimode operation); U.S. Pat. No. 4,141,546 (describing a mini-collator/sorter); U.S. Pat. No. 4,012,032 (describing a sheet handling system with a receiving tray for use in non-collate mode and a plurality of collator bins for operating in collator mode); U.S. Pat. No. 4,026,543 (describing a control system using a copy count, a tangent copy count, and a document tracing indicator to provide automatic control for copy overflows); U.S. Pat. No. 4,134,581 (describing a system having multiple collator bins treated as one virtual bin).
In these systems there are generally two approaches to increasing output catch tray capacity. The first approach uses multiple receipt trays, bins or mailboxes (for simplicity, collectively referred to as xe2x80x9ctrays). The trays may be vertically or horizontally repositionable relative to a fixed output port, or the copier output port may be vertically or horizontally repositionable relative to a fixed tray or trays, or some combination of movable trays and moveable output port may be employed. However, although though multiple trays are in use, the individual trays generally have limited capacities requiring either additional control for tray switching, system shut-down or additional operator intervention.
In the second approach a single large output catch tray is used, but relatively powerful, complicated and expensive elevator mechanisms are required either to lower the catch tray or raise the copier output port as the stack grows in order to keep the top of the stack within an acceptable range below the sheet output port. So far as is presently known, prior art does not include the combination of a single large output catch tray with a vertically repositionable output port.
Other systems such as U.S. Pat. No. 3,871,643 teach a sorter system having two sorter sections. In particular, the control switches from one section to the next to continue a copying job. In addition, if the bins in both sections of the sorter contain copy sheets, and the job requirement has not been completed, upon removal of the copy sheets in one of the sections, the reproduction machine will resume operation after having been temporarily halted.
The addition of multiple bins and, trays, catch trays with elevator mechanism, or vertically repositionable copier output port increases the complexity of the components for copiers and their controls, with a corresponding decrease in expected reliability and increase in cost. It would therefore be desirable to provide a high capacity output catch tray for document production machines such as photocopiers, printers and fax machines having a minimum number of receiving trays and/or complex mechanisms and yet be able to handle high volume requirements with minimum operator intervention. Due to the lack of such a device, it is not unknown in the prior art to use stacks of cardboard boxes as cheap, high capacity output xe2x80x9ctrays.xe2x80x9d
B. Inclined Output Trays
For better stacking alignment to obtain neat, square and even-sided stacks, as is known in the art, it is preferable to output sheets or sets sequentially onto an inclined surface. Initially this is the indined surface of the empty output tray, and then it is the correspondingly inclined upper surface of the sheet or set previously stacked thereon. If the output tray surface is upwardly inclined away from the copier output port into the tray, this is known in the art as xe2x80x9cuphillxe2x80x9d stacking. It is called xe2x80x9cdownhillxe2x80x9d stacking if the output tray slopes downwardly away from the copier output port. There are many advantages to using either xe2x80x9cuphillxe2x80x9d or xe2x80x9cdownhillxe2x80x9d stacking, either for stacking per se, or for stacking in a compiler for stapling or other binding or finishing. It allows different sizes of sheets to be stacked using the same paper path and the same tray system, using gravity assisted stacking against a simple inboard or outboard alignment surface, and is therefore relatively less expensive than more complicated active stacking registration or alignment systems, such as those requiring scullers, flappers, tampers, joggers, etc.
xe2x80x9cUphillxe2x80x9d stacking desirably lends itself to stacking alignment at an inboard side of the output tray, that is, at the side adjacent the copier. It automatically slows down the ejected sheets, due to their initial xe2x80x9cuphillxe2x80x9d movement. The sheets then reverse their movement to slide back down against an upstanding wall or edge adjacent to but underlying the output port. Incoming sheets thus do not get caught on the edge of the stack in the tray, so long as subsequent sheets or sets enter above the top of the stack, which of course grows in length/height as the copy job progresses.
Prior art does not provide for a high capacity single output tray which can quickly and easily be configured to provide uphill, horizontal or downhill output stacking without the use of a tray elevator or vertically repositionable sheet output port.
C. Stack Edge Alignment
It is known in the art to provide a stacking system with an output tray elevator. The top of a stack in the output tray is maintained at a suitable height for such stacking, by the output tray and all its contents being moved downward as the stack accumulates, so that the top of the stack remains in the same general relative position below the copier output port.
In prior art, the stacking alignment surface is normally a fixed vertical surface which does not move relative to the copier and its output port, and not an integral upstanding side of the tray itself, as in a sorter bin or other conventional stacking tray. That is, the alignment surface against which the ejected sheets or sets are aligned is typically the vertical surface of the side of the machine or the stacking tray elevator itself, against which the sheets or sets may align as they stack.
In part, such a fixed alignment surface addresses the problem that if, instead, a conventional alignment side wall integral (and substantially perpendicular to) the stacking tray were provided (moving therewith), that alignment wall require a height equal to the full elevator travel range of the output tray. Otherwise, sheets or sets stacked higher than that alignment wall would slide off the stack. In the empty, fully raised position of such an output tray, such a fixed height alignment side wall would unacceptably extend well above the top of the machine, and/or block the sheet entrance to the tray if located on that side of the tray for xe2x80x9cuphillxe2x80x9d stacking.
Also, with such an output tray designed for high capacity stacking, the first incoming sheets would be required to drop a substantial distance before coming to rest on the top of the stack or tray. This large drop distance tends to increase the number of stacking problems noted above, such as sheets or sets coming to rest in an orientation other than flat against the top of the stack, and/or substantial scatter within the stack.
However, previous systems with fixed alignment surfaces suffer from various drawbacks. Since the edges of the sheets in the stack move relative to the alignment surface, friction of the sheet edges against the alignment surface lifts the sheet edges relative to the downward motion of the output tray, abrading the sheet edges and disturbing the stack so that is less flat, neat and square. This phenomenon is known in the art as xe2x80x9ccreep.xe2x80x9d With the extended use experienced by high volume copiers, over time, the friction also causes wear on the alignment surface so that it may become less smooth, exacerbating the problems of lift and creep. Fixed alignment surfaces must also be relatively long to provide high capacity and are therefore relatively bulky.
One previous attempt to deal with the problem of fixed alignment surfaces can be seen in U.S. Pat. No. 5,346,203, in which a variable height stack registration and edge alignment system is provided by way of numerous small belt-like flexible sheets which unroll upward corresponding to upward movement of a vertically repositionable sheet output port. However, as with previous tray elevator systems, this system is subject to the drawbacks of complexity, expense, and limited inter-connectivity; even more so in that it is associated with multiple output tray and/or mailbox systems.
It is therefore desirable to provide a simple, relatively smooth, variable length stack alignment and edge alignment system which corresponds directly and automatically to the output tray height and requires no external power source or control system.
To recapitulate, the limitations of the prior art of high capacity output trays are substantial. A simple fixed high capacity output tray without a vertically repositionable sheet output port is impractical because it requires either a high fixed side wall or that the output tray be very deep, so that ejected sheets or sets would have too far to drop and be subject to the abovementioned problems of scatter, disorientation, buckling, folding, etc. Vertically repositionable copier output ports, output tray elevators, multiple trays/bins/mailboxes are all relatively complex and high maintenance, require external power sources and controls, and are correspondingly expensive both initially and over time.
The present invention provides a simple, high capacity, adjustable, sheet stacking output tray suitable for connection to both large, high volume copiers and to smaller, less expensive ones, which is capable of automatically maintaining the top of stack height within an acceptable range relative to the sheet output port, without external power source or control, where precise stack height control is not required. The various adjustments in output tray angle, stack angle, effective spring rate, total weight capacity, and total stack height permitted by the invention allow a user to customize and optimize the invention for numerous applications. The invention thus uniquely provides for maximum upgrade-ability, downgrade-ability and compatibility between various sizes, types and brands of document production devices.
Briefly, the present invention is concerned with a simple, inexpensive high capacity output catch tray. The disclosed output tray automatically increases in capacity as the stack of copies in it accumulates, without external power source or control, while maintaining a relatively constant elevation relative to the copier output port, and automatically returns to its original position when partially or completely unloaded.
The invention achieves these advantages by the use of trampolinetype arrangement that suspends a stack support platform by springs around its perimeter from a frame removeably attached to the copier. As copies accumulate on the platform the weight of the copies causes the springs stretch and increases the capacity of the output tray. The springs act as energy-storing biasing elements which return the platform to its unloaded position when the stack of copies is removed from the tray, and may also act as variable length alignment surfaces to keep the accumulating stack neat and square. Preferably the springs have a relatively smooth outer surface such as is provided by telescoping cylindrical sleeves around metallic coil springs, elastic cords or bands, or bungee cords, to keep the sides of the stack straight and prevent the sheets from binding or rubbing as the stack increases in length, thereby minimizing lift or creep of the sheets relative to the platform and alignment surface, but other commonly known biasing devices such as weights and pulleys, could be used alone or in combination with springs.
The invention provides improved output stacking of multiple printed sheets, such as multiple sets or jobs of flimsy copy sheets sequentially outputted by a copier, with overall stack alignment for subsequent handling, particularly for large stacks, at relatively low cost, and without sacrificing desired stacking and alignment orientations. Further so disclosed is a stacking system with a variable length alignment surface coupled to a vertically movable stack support platform.
The invention has particular utility and application for high capacity stacking of pre-collated copy output sheet sets from a copier, which may include a compiler and finisher, where such output may require stacking relatively large numbers of completed copies in a relatively high stack. Such stacked copies may be individual sheets or sets which may be unfinished, or may be stapled, glued, bound, or otherwise finished and/or offset.
The invention further provides a high capacity output tray for stacking substantial quantities of the output from a copier on a support platform optionally providing an inclined stacking surface at a substantial angle from the horizontal for receiving and aligning sheets against an upright stack edge alignment surface. Here, with little or no relative movement between the alignment surface and the stack edge, this stack edge alignment surface is automatically varied in length below the copier output port and above the stack support platform in coordination with the change in stack length/height supported by the platform.
The invention overcomes the above and other problems and limitations of prior art, without requiring an externally powered tray elevator or variable height output port, yet without sacrificing the desired output and stacking positions for the ejected sheets or sets.
The copier may operate in a single mode producing simple stacks, or may operate in multiple modes with stacks, unstapled sets and/or stapled sets, the sets and stacks being offset in the catch tray. With the addition of a simple detector, the copier can be made to temporarily halt when the top of the stack reaches a specified height relative to the sheet output port to avoid spilling or jamming, then resume operation and continue to do so as the output tray is emptied until the job in process is either completed or canceled.
As to specific hardware components which may be used with the subject apparatus, or alternatives, it will be appreciated that, as is normally the case, various suitable such specific hardware components are known per se in other apparatus or applications, including the cited references and commercial applications thereof.